Experimental Study of Strain Measurement using 2D Digital Image Correlation on Fixation Plate and Calcaneus Bone Fracture

Abstract

The plate and screw internal fixation technique is widely used for the treatment of fractured bones. Determining the mechanical behavior of bone plates under load conditions remains challenging, as it is anisotropic, non-linear, and inhomogeneous. Bone strain is frequently measured using strain gages, but they can only measure the strain at a single point. The optical method known as digital image correlation (DIC) provides the displacement and consequently the strain over the entire region of interest on the bone surface. The objective of this study was to investigate the strain changes in the surface of a calcaneus plate fixation during load compression using the digital image correlation method. In this study, a two-dimensional digital image correlation (2D-DIC) and strain gauges-based experimental methodology for calculating calcaneal plate strains is presented. A 500 N static load was applied to a synthetic calcaneus that was both plate-covered and intact. A Sanders type II fractured calcaneus was stabilized with stainless steel (316L) plate. At the same locations on the calcaneus plate, displacement and strains were recorded. According to the results of the DIC method, the maximum strain values along the x, y, and shear directions were 0.008, 0.010, and 0.012 mm, respectively, while the measurement result for the strain gauge was 0.0015 mm. The experimental result had a slightly lower strain gauge than the DIC method’s output. The results of the experiment and the DIC were thought to be in good agreement.